The present invention relates to adapter circuits for providing an interface between an input port and a plurality of input devices. The adapter circuit has particular application to the input ports of video games.
In the typical video game there is provided a video monitor, which may be a computer terminal or a television set, for example. A program unit, which may be built into a computer or provided in a separate housing, contains the game software for generating the video display and a cursor or "blip" which moves about the display. There are also provided one or more controllers usable by the player or players for controlling movement of the cursor on the video screen. The controller is adapted to be plugged into the computer or separately housed program unit. There are typically accommodations for two identical controllers so that a game can be played by two competing players at a time.
Commonly, each computer or program unit is adapted for use with a number of different game programs. Different types of controllers have been designed for use with different types of game programs, since the nature and speed of cursor movement required can differ considerably from game to game. Thus, for example, there have been developed "paddle"-type controllers, which utilize a rotating knob for a one-dimensional control of cursor direction; joystick-type controllers which utilize a joystick for two-dimensional control of cursor direction; trackball-type controllers which utilize a universally rotating ball for two dimensional control of both speed and direction of cursor movement; and touch tablet controllers which respond to movement of the user's finger over a tablet representative of the video screen to produce a corresponding cursor movement.
To realize the full potential of a video game system, the user should have a pair of each of these types of controllers. But this necessitates that the controllers must be repeatedly connected and disconnected each time a different type of controller is needed. There have been provided port expansion adapters which are connected to the video game input port and to each of the several different types of controllers to obviate connection and disconnection of the controllers. In such adapters, when a particular type of controller is to be used, a selective operation must be performed to render the selected controller operative for controlling the game. This selection operation may take the form of typing in on a keyboard information identifying the selected controller, or activating selector switches or the like. Such units are inconvenient in that they require the user to remember the proper selection operation sequence for each type of controller. Thus such adapters are susceptible to erroneous connections, wherein the player attempts to enable one controller and in fact enables another.